Can ts shapes be interactive and control years choices?

[remicousin]

Sort of what I did in wat_bal to click a time series point to have the map plot it. Clicking and dragging the vertical lines could update the controls. Sticky points:

1. would be to choose years only, not seasons, so would need some sort of year_snap functionality for the vertical line to snap at the right spot
2. would need a pop-up to show what year the line is in as one drags it
3. how would that interact with the submit button those controls are otherwise part of?